Electrical energy generated by various methods can be difficult to store efficiently. Chemical batteries, hydraulic pumping, and water splitting suffer from low energy-density storage or incompatibility with current transportation infrastructure. UCLA researchers have demonstrated a method for storing electrical energy as chemical energy in higher alcohols, which can be used as liquid transportation fuels.
"The current way to store electricity is with lithium ion batteries, in which the density is low, but when you store it in liquid fuel, the density could actually be very high," James Liao, UCLA's Ralph M. Parsons Foundation Chair in Chemical Engineering, said. "In addition, we have the potential to use electricity as transportation fuel without needing to change current infrastructure."
Liao and his team genetically engineered a lithoautotrophic microorganism known as Ralstonia eutropha H16 to produce isobutanol and 3-methyl-1-butanol in an electro-bioreactor using carbon dioxide as the sole carbon source and electricity as the sole energy input.
Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. There are two parts to photosynthesis — a light reaction and a dark reaction. The light reaction converts light energy to chemical energy and must take place in the light. The dark reaction, which converts CO2 to sugar, doesn't directly need light to occur. "We've been able to separate the light reaction from the dark reaction and instead of using biological photosynthesis, we are using solar panels to convert the sunlight to electrical energy, then to a chemical intermediate, and using that to power carbon dioxide fixation to produce the fuel," Liao said. "This method could be more efficient than the biological system."